In today's information generation, the computer has become an indispensable electronic information product in everyone's life. The peripheral input device of the computer includes a mouse, a keyboard, a writing board, or the like. Amongst those devices, the keyboard plays an irreplaceable role because it allows user to rapidly input characters and symbols into the computer, and allows user to edit plural document files at the same time.
FIG. 1 is a schematic perspective view illustrating the appearance of a conventional keyboard. The conventional keyboard 1 is used for being built in a laptop, and consists of a base portion 11 and plural keys 10. The arrangement of the keys 10 is determined according to the design of the manufacturer. When any of the keys 10 is pressed by user's finger, a corresponding character, symbol or number is entered.
FIG. 2 is a schematic cross-sectional view illustrating a conventional keyboard. As shown in FIG. 2, the keyboard 1 comprises the base portion 11 and the plural keys 10. Each key 10 comprises a keycap 101, a scissor connecting element 102 and an elastomer 103 aligned with the keycap 101. The scissor connecting element 102 is connected to the keycap 101, and also connected to the elastomer 103. The base portion 11 comprises a membrane switch circuit 12, plural spacing structures 13, a supporting plate 14 and a lower casing 15. The membrane switch circuit 12 comprises an upper wiring board 121, a separation layer 122 and a lower wiring board 123, all of which are made of a light-transmissible material. The membrane switch circuit 12 further comprises plural key switches 124, each of which corresponds to a key 10 and is configured to be aligned with the center of the elastomer 103 of the corresponding key 10. Once the keycap 101 of any one of the keys 10 is pressed down, the two interlock pieces of the scissor connecting element 102 swings and depresses the elastomer 103, therefore triggering the corresponding key switch 124 disposed on the membrane switch circuit 12. Consequently, the triggered key switch 124 generates output signals.
Please refer to FIG. 2 again. The supporting plate 14 is located under the membrane switch circuit 12 for supporting it. The lower casing 15 wraps the supporting plate 14 and the membrane switch circuit 12 for protecting them. The plural spacing structures 13 are disposed on the membrane switch circuit 12, each of which is arranged between every two adjacent keys 10. An accommodation space 131 is consequently formed between each two adjacent spacing structures 13 for receiving the scissor connecting element 102 and the elastomer 103 of each key 10. The keycap 101 of the key 10 is supported by the scissor connecting element 102 and the elastomer 103, therefore having an altitude higher than the altitude of the spacing structure 13. When the keycap 101 is pressed down, the two interlock pieces of the scissor connecting element 102 swings and the elastomer 103 is subjected to downward deformation to trigger the key switch 124. Under this circumstance, the altitude of the keycap 101 is lowered in response to the pressing force of the user, sinking into the accommodation space 131. However, when the keycap 101 is no longer pressed by the user, the elastomer 103 is subjected to upward deformation in response to the elastic force of itself, and the keycap 101 is returned to its original position. Meanwhile, the scissor connecting element 102 also goes back to its initial state and supports the keycap 101 as a level higher than the spacing structure 13, protruding out from the accommodation space 131.
Nowadays, the trends of designing electronic devices are toward small size, light weightiness and easy portability. Above-mentioned structure of the conventional keyboard 1 has a fixed height, so it is difficult to reduce the altitude of the overall keyboard 1 and the product with the conventional keyboard 1 is heavy and large.
Therefore, there is a need of providing an improved low-profile keyboard in order to overcome the drawbacks of the conventional technologies.